The invention is concerned with a method of modulation of laser generation with continuous pumping of an oxygen-iodine laser especially, and with a device for performing this method.
Modern technological lasers with outputs of hundreds and thousands of watts are characterized by their multifunction ability, i.e., by the possibility to operate in both continuous and periodically pulsed regimes. A periodically pulsed regime is important for some laser technology of material processing (e.g. cutting, drilling, etc.). High-power CO.sub.2 gas lasers and solid-state Nd:YAG lasers are the typical representatives used for these purposes till now. A chemical oxygen-iodine laser (hereinafter called COIL) which could be able to compete with the above mentioned lasers in the future has not had this possibility so far. Related iodine photodissociation lasers (IPL) can operate both in the continuous and pulsed regime. However, for the time being, their output power has not exceeded 10 watts only and efficiency is very low (about 0.1%). For these reasons, their use for technological purposes is hardly probable. Another related iodine laser working with a combined pumping (i.e. a combination of chemical and photodissociation pumping or chemical and discharge pumping-(ICL)) has all the subsystems of a COIL except for I.sub.2 injection, instead of which they use the dissociation of perfluoralkyliodides. This makes these systems more complicated and rather expensive for industrial applications. These lasers operate in a pulsed regime only and, moreover, the subsystem of the iodides dissociation by means of either flashlamps or open discharges has a limited lifetime which would be reduced to several hours of operation in case of high repetition rates of 100-1000 Hz. A chemical oxygen-iodine laser (COIL) is the only type of iodine laser which can generate kilowatt output powers in cw (continuous wave) regime at the wavelength of 1.315 .mu.m. However, a suitable method of modulation of its generation has not been worked out till now.
A Q-switching technique of the mechanical type (see F. Matsuzaka, T. Ohga, M. Imachi, T. Uchiyama "Q-switching Operation of Chemical Oxygen Iodine Laser", Proceedings of the 12th International Conference on Lasers and Applications, New Orleans, USA, pp. 223-227, Dec. 3-8, 1989) or the magnetic-optical type (see R. Highland, P. Crowell, G. Hager "A 630 Watt Average Power Q-switched Chemical Oxygen-Iodine Laser", Proceedings of the 12th International Conference on Lasers and Applications, New Orleans, USA pp. 228-236, Dec. 3-8, 1989) have been used for pulsing in cw COIL, nevertheless, these methods have substantial disadvantages. A COIL system is characterized by a low gain, a low output coupling and a near threshold generation (compared with IPL and ICL), therefore, the techniques and methods which could increase the intraresonator losses are not suitable. A piezoelectric modulation of mirror position to get a pulsed regime would be problematic because a COIL of usual construction has internal spherical mirrors and pressure differences between the inner and outer sides of the mirrors is 100 kPa approximately. A pulse injection technique (e.g. by means of IPL) is possible theoretically but it has not been realized. A pulsing of the chemical pumping seems to be unsuitable for this purpose, too.
Two patents related to COIL found in available databases do not deal with an appropriate method of modulation of generation in this type of laser. One of them, U.S. Pat. No. 4,653,062, concerns a new construction for introducing and mixing of singlet oxygen and iodine monochloride which differs from a usual source of atomic iodine in the sense that it enables an increase of duct pressure in the laser. Another U.S. Pat. No. 4,780,880 solves the question of enhancing the laser action in COIL wherein a gas stream having a desired reactant gas concentration profile is combined with a diluent gas concentration profile using hydrogen as the diluent gas.